In the field of passenger transport, for example in the case of aircraft, railways, or motor vehicles, the comfort of passengers is considerably improved if sanitary units, for example toilets, are provided. In aviation it forms part of the state of the art to arrange at least one central device for drainage, for example a so-called drain mast, in order to be able, during the flight, to centrally drain to the outside of the aircraft the gray water arising from the use of hand basins. Moreover, it is common practice to arrange a central fresh-water system, for example in order to supply basins, toilets or other consumers of water, for example the galley.
From DE 102 29 799 A1, for example, a central fresh-water/waste-water system is known in which a central gray-water system is provided which may either be drained by way of a central drain mast or, after a treatment stage, may be reused for flushing toilets.
Furthermore, from GB 964,971 a toilet unit, in particular for aircraft, is known. The waste water is reused in a so-called recirculation system. In this manner the water arising from the toilet may be filtered and re-used for flushing the toilet. The above-mentioned toilet unit may either be serviced on board the aircraft, or may be removed from the aircraft for servicing.